With increasing popularity of mobile voice and data communication, there is an ever increasing demand for high-speed voice and data communication. The licensed spectrum for cellular communication is rapidly being exhausted by a dense and growing subscriber base. This applies in particular to the valuable low-frequency bands with low propagation loss traits.
A significant amount of unlicensed spectrum or unlicensed bands is available. For illustration, a significant amount of spectrum is globally available in the 5 GHz frequency band. Within the Long Term Evolution (LTE) radio access technology as specified by the Third Generation Partnership Project (3GPP), it is desirable to employ the unlicensed bands. It is desirable to utilize the License Assisted Access-LTE (LAA-LTE) procedure to augment the capacity of licensed frequency bands in the unlicensed bands. LAA-LTE may be used for carrying data traffic for mobile services. The purpose of LAA-LTE is to extend LTE cellular communication to the unlicensed spectrum. Sometimes, LAA-LTE is also referred to as LTE-unlicensed (LTE-U).
In the licensed frequency bands, there is typically operator control over resource management both in frequency and time domain. This is referred to operator-controlled network deployment. Further, transmission may be protected by employing Automatic Repeat Request (ARQ) schemes. Typically, the resource management and/or the ARQ scheme is implemented to a significant degree in the Data Link Layer comprising the Medium Access (MAC) layer, according to the Open System Interconnection (OSI) Model standardized by the International Telecommunication Union (ITU).
Employing LAA-LTE or transmission of data packets typically faces restrictions in terms of transmission reliability. Protection of successful transmission may be possible to a limited degree only. E.g., if compared to the licensed spectrum, the ARQ process can be less predictable, as the medium is shared in a more or less uncontrolled manner between different parties. E.g., the transmission channel in the unlicensed band could be used by third parties. E.g., the unlicensed band could be used by other network providers, private persons and other business segments. Third parties could employ LTE, Wireless Local Area Network (WiFi), radar and/or other communication problems. The so-called hidden node problem may occur where the transmitting device may not be able to detect interfering radio signals.